1. Field of the Invention
The present invention relates generally to the field of mechanical lifts including linear actuator systems, and more particularly to a wheelchair lift platform structure having stacking platform sections capable of being folded and stored in an upright position within a vehicle.
2. Description of the Related Art
Vehicular wheelchair access systems for handicapped persons, such as lifts and ramps, can be mounted on vehicles and made deployable/stowable with respect to the vehicle. Wheelchair users typically move their wheelchair along the lift or ramp platforms in order to transfer from the ground to the vehicle and from the vehicle to the ground using a lift mechanism and platform structure or ramp, which may be operated mechanically, electrically, pneumatically or hydraulically, etc. Known wheelchair lift platform structures include solid rigid panels or floors as platform structures that must be stowed away within the vehicle itself. Accordingly, the wheelchair access system is used in conjunction with and occupies a portion of the floor space of the vehicle and further may obstruct passageways and restrict the amount of available space within the vehicle.
For handicapped persons, mobility is enhanced with the availability of wheelchair access systems that are powered to provide much or all of the movement of the motorized platform structure. This is particularly useful due to the inconvenience of physical activity by the wheelchair passenger. Such lifts typically have pivotal mechanisms for raising and lowering platform structures, see e.g., U.S. Pat. No. 5,261,779 to Goodrich for “Dual Hydraulic, Parallelogram Arm Wheelchair Lift” issued 16 Nov. 1993 and U.S. Pat. No. 6,238,169 to Dupuy, et al. for “Dual Function Inboard Barrier/Bridge Plate Assembly for a Wheelchair Lift” issued 29 May 2001 to applicant's assignee. Each of these discloses dual hydraulic, parallelogram arm wheelchair lift assemblies for use typically in commercial vehicles. The lift assembly has a platform connected to a parallelogram structure. In both of the above assemblies, when the platform of the lift is in a stowed position, the platform essentially blocks the doorway. Moreover, the wheelchair access system being fixed on the floor of the vehicle itself may provide limited space and visibility from and within the vehicle.
Other wheelchair lifts that do not completely block the door when in a stored position have been described, e.g., U.S. Pat. No. 4,664,584 to Braun, et al. for “Rotary Wheelchair Lift” issued 12 May 1987 discloses a rotary hydraulic lift having a vertically-telescoping slide tube and a horizontal wheelchair platform support arm attached to the lower end of the slide tube moving the platform into or out of the vehicle parallel to the slide tube. However, the platform structure and pivotal mechanism employed in rotatable wheelchair lifts require a substantial amount of space.
Further, foldable and multiple section platform assemblies are known to decrease the platform area. Known examples of platform structures employing hinges between inner and outer platform sections such that the outer section pivots and folds against the outer side of the inner section include U.S. Pat. No. 6,379,102 to Kameda for “Wheelchair Lift with Foldable Platform” issued 30 Apr. 2002. A lack of predictability of operation while being folded or unfolded, however, is a substantial disadvantage associated with this type of platform assembly when the platform structure is deployed from its stowed position. For example, in the stowed position the outer platform section, unless properly hooked, can dangle and assume a variety of positions. Rollstops to prevent the wheelchair passenger or operator from interaction with the lift structural componentry have either not been provided or are not effective. Additionally, exposed rigid linkages may come in contact with the operator or passenger. Such linkages, in addition to being unsightly and annoying, may also present a substantial safety hazard to passengers and operators who come into contract with them during the operation of the lift.
To address the growing concern for passengers who are handicapped or otherwise have limited mobility, it would be desirable to provide compact, storable wheelchair access systems that minimize the space they occupy on the floor of the vehicle for storing the lift platform structure. Further, in certain instances it would be desirable for the access system to provide for enhanced access to the door and particularly the door window for unobstructed views from within the vehicle. In view of the foregoing, there remains a need for a wheelchair-lifting platform that can be stored upright and out of the way inside the vehicle when not in use, while occupying a minimum amount of stored space.